According to the recent trend of lighting technology, an LED has been employed as a light source, in order to reduce energy.
A high-brightness LED is differentiated from other light sources in terms of various aspects such as energy consumption, lifetime, and light quality.
However, since the LED is driven by a current, a lighting apparatus using the LED as a light source requires a large number of additional circuits for current driving.
In order to solve the above-described problem, an AC direct-type lighting apparatus has been developed.
The AC direct-type LED lighting apparatus generates a rectified voltage using a commercial AC power supply and drives an LED. Since the AC direct-type LED lighting apparatus directly uses the rectified voltage as an input voltage without using an inductor and capacitor, the AC direct-type LED lighting apparatus has a satisfactory power factor.
A general LED lighting apparatus is designed to be driven through a voltage obtained by rectifying commercial power having an AC voltage.
A lamp of the LED lighting apparatus includes a large number of LEDs connected in series to each other, and controls the LEDs connected in series to emit light using the rectified voltage.
Recently, the LED lighting apparatus has employed a dimmer using a triac, in order to control brightness. The dimmer is generally used to control the brightness of an incandescent lamp.
When the dimmer is applied to the LED lighting apparatus, there may occur a difference between a design value of the LED lighting apparatus and the characteristic of the triac used as a part of the dimmer.
The triac of the dimmer has a holding current which may be changed in response to the characteristic difference. Thus, when a low-angle rectified voltage is provided to the LED lighting apparatus employing the dimmer including the triac, an insufficient level thereof may cause a flicker.
Furthermore, according to the characteristic and use environment of the triac included in the dimmer, a rectified voltage having an abnormal waveform may be inputted to the lamp at the initial stage.
When the rectified voltage having an abnormal waveform is inputted to the lamp, a flicker may occur in the initial state where the LED lighting apparatus is driven.
The conventional LED lighting apparatus must reduce the occurrence of the flicker, in order to perform the brightness control function using the dimmer including the triac.